Facebook was launched from Mark Zuckerberg’s dorm room 13 years ago today (it was called thefacebook back then), yet there is still no DISLIKE button after all these years. But when should the billionaire CEO celebrate Facebook’s birthday: when he first registered the URL for thefacebook.com, when he created the first Facebook profile while the site was in beta, or when Zuckerberg and his fellow cofounders filed the legal paperwork to incorporate their company. (Thanks to Dino Grandoni for pointing out these alternative Facebook birthdays to us.)